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BUG: KCSAN: data-race in bio_endio / blk_throtl_bio

read to 0xffff88809b7f8d94 of 2 bytes by interrupt on cpu 1:
 bio_remaining_done block/bio.c:1760 [inline]
 bio_endio+0x3e/0x400 block/bio.c:1790
 req_bio_endio block/blk-core.c:245 [inline]
 blk_update_request+0x427/0x7b0 block/blk-core.c:1464
 scsi_end_request+0x6b/0x360 drivers/scsi/scsi_lib.c:576
 scsi_io_completion+0x11d/0xc80 drivers/scsi/scsi_lib.c:960
 scsi_finish_command+0x283/0x380 drivers/scsi/scsi.c:228
 scsi_softirq_done+0x259/0x280 drivers/scsi/scsi_lib.c:1476
 blk_done_softirq+0x1eb/0x250 block/blk-softirq.c:37
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 do_IRQ+0x81/0x130 arch/x86/kernel/irq.c:263
 ret_from_intr+0x0/0x21
 arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
 _raw_spin_unlock_irqrestore+0x51/0x80 kernel/locking/spinlock.c:191
 spin_unlock_irqrestore include/linux/spinlock.h:393 [inline]
 pagevec_lru_move_fn+0x13e/0x180 mm/swap.c:214
 __pagevec_lru_add mm/swap.c:985 [inline]
 __lru_cache_add+0x120/0x1d0 mm/swap.c:411
 lru_cache_add+0x1f/0x30 mm/swap.c:447
 add_to_page_cache_lru+0x16a/0x260 mm/filemap.c:959
 pagecache_get_page+0x2ac/0x6f0 mm/filemap.c:1682
 grab_cache_page_write_begin+0x5d/0x90 mm/filemap.c:3259
 ext4_da_write_begin+0x1a3/0x840 fs/ext4/inode.c:2965
 generic_perform_write+0x136/0x320 mm/filemap.c:3309
 ext4_buffered_write_iter+0x143/0x290 fs/ext4/file.c:252
 ext4_file_write_iter+0xf4/0xd40 fs/ext4/file.c:547
 call_write_iter include/linux/fs.h:1902 [inline]
 new_sync_write+0x388/0x4a0 fs/read_write.c:483
 __vfs_write+0xb1/0xc0 fs/read_write.c:496
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff88809b7f8d94 of 2 bytes by task 12238 on cpu 0:
 bio_set_flag include/linux/bio.h:239 [inline]
 blk_throtl_bio+0x162/0x1a90 block/blk-throttle.c:2270
 blkcg_bio_issue_check include/linux/blk-cgroup.h:602 [inline]
 generic_make_request_checks+0x6fa/0x1040 block/blk-core.c:964
 generic_make_request+0x3e/0x700 block/blk-core.c:1020
 __blk_queue_split+0x779/0xc40 block/blk-merge.c:347
 blk_mq_make_request+0x104/0xf60 block/blk-mq.c:1920
 generic_make_request block/blk-core.c:1066 [inline]
 generic_make_request+0x196/0x700 block/blk-core.c:1008
 submit_bio+0x96/0x3c0 block/blk-core.c:1192
 ext4_io_submit+0xdf/0x110 fs/ext4/page-io.c:384
 io_submit_add_bh fs/ext4/page-io.c:425 [inline]
 ext4_bio_write_page+0x480/0xb4e fs/ext4/page-io.c:543
 mpage_submit_page+0xe4/0x1a0 fs/ext4/inode.c:2075
 mpage_map_and_submit_buffers+0x3c4/0x6c0 fs/ext4/inode.c:2319
 mpage_map_and_submit_extent fs/ext4/inode.c:2458 [inline]
 ext4_writepages+0x1449/0x2500 fs/ext4/inode.c:2771
 do_writepages+0x6b/0x170 mm/page-writeback.c:2344
 __filemap_fdatawrite_range+0x1c5/0x230 mm/filemap.c:421
 generic_fadvise+0x4a0/0x4b0 mm/fadvise.c:115
 vfs_fadvise+0x92/0xa0 mm/fadvise.c:187
 ksys_fadvise64_64+0x61/0xa0 mm/fadvise.c:201
 __do_sys_fadvise64 mm/fadvise.c:216 [inline]
 __se_sys_fadvise64 mm/fadvise.c:214 [inline]
 __x64_sys_fadvise64+0x5e/0x80 mm/fadvise.c:214
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12238 Comm: syz-executor.1 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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